Poly-alpha-olefins containing a combination of dialkyl-3, 3&#39;-thiodipropionates, alkylidenebisphenols and phenyl salicylates



United States Patent fitice 3,633,814 Patented May 8, 1962 Clarence E. Tholstrup, Kingsport, Tenn, assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Jan. 25, 1960, Ser. No. 4,189 17 Claims. (Cl. 260-4585) This invention relates to new poly-a-olefin compositions. Preferred embodiments of the invention relate to polyethylene and polypropylene compositions having improvide stability at elevated temperatures to oxidative degradation.

Poly-a-olefins such as polyethylene, polypropylene and the like are commonly subjected to elevated temperatures in the course of their processing into useful items of commerce. Such processing methods as rolling, injection molding, extrusion and the like at elevated temperatures usually result in oxidative degradation of the polymer. In addition, many uses of poly-a-olefins, such as in electrical insulation and the like, often times expose the polya-olefin to elevated temperatures. To minimize oxidative deterioration in poly-u-olefins, antioxidants or stabilizers are often times incorporated therein.

It is an object of this invention to provide new poly-aolefin compositions having improved resistance to thermal degradation.

It is another object of this invention to provide new synergistic combinations of stabilizers for poly-oz-olefin compositions.

It is also an object of this invention to provide novel polyethylene and polypropylene compositions containing synergistic combinations of compounds that improve the stability of the polyethylene and polypropylene compositions against deterioration resulting from exposure to elevated temperatures and ultraviolet light.

Other objects of the invention will be apparent from the description and claims that follow.

The present invention comprises poly-a-olefin compositions having incorporated therein a stabilzer combination of a diester of 3,3-thiodiopropionic acid, an alkylidenebisphenol and a phenyl salicylate.

The diesters of 3,3'-thiodipropionic acid comprising the present stabilizer combination have the following formula:

II S (CH2OH2COR):

wherein R is an alkyl radical having at least 4 and generally 4 to 20 carbon atoms, with 8 to 18 carbon atoms being preferred. A particularly effective ester has twelve carbon atoms for the R substituent, namely, dilauryl 3,3- thiodipropionate. However, any diester of 3,3'-thiodipropionic acid as described above can be employed in the present stabilizer combination including the butyl, amyl, hexyl, heptyl, octyl, monyl, decyl, tridecyl, myristyl, pentadecyl, cetyl, heptadecyl, stearyl, and eicosyl diesters of 3,3-thiodipropionic acid, or mixtures thereof.

A wide variety of alkylidenebisphenols can be effectively utilized in the present stabilizer combinations, particularly those described in the copending application by Joyner, Shearer and Tholstrup Serial No. 850,985, filed November 5, 1959. A particularly eliective group of alkylidenebisphenols have the following formula I la R3 wherein R is an alkylidene radical having 1 to 12 carbon atoms, and wherein R R R and R are hydrocarbon radicals having 1 to 12 carbon atoms including benzyl radicals, cyclohexyl radicals, l-alkylbenzyl radicals, 1- alkylcyclohexyl radicals, or more usually alkyl radicals having 1 to 12 and preferably 1 to 4 carbon atoms. R and R are desirably tertiary alkyl radicals having 4 to 8 carbon atoms.

The phenyl salicylate component of the present stabilizer combinations likewise can be widely varied, and includes phenyl salicylates having the following formula wherein R and R are hydrogen atoms or hydrocarbon radicals having 1 to 15 carbon atoms including benzyl radicals, cyclohexyl radicals, l-alkylbenzyl radicals, lalkylcyclohexyl radicals, or more usually alkyl radicals having 1 to 15 carbon atoms. Suitable substituted phenyl salicylates that can be utilized include those described in the copending application by Addelburg, Lappin and Rouse, Serial No.'775,336, filed November 21, 1958.

The combination of the described diesters of 3,3'-thiodipropionic acid, alkylidenebisphenols and phenyl salicylates can be used to stabilize a wide variety of solid poly-a-olefin compositions against deterioration resulting from exposure to elevated temperatures. Any of the normally solid polymers of a a-monoolefinic aliphatic hydrocarbons containing 2 to 10 carbon atoms can be stabilized in accordance with the invention. The subject stabilizer combinations are preferably .used in polyethylene and polypropylene, although such poly-a-olefins as poly(3- methylbutene-l poly(4-methylpentene-l poly(pentenel), p0ly(3,3-dimethylbutene-l poly(4,4-dimethylbutene- 1), poly(octene-l), po1y(decene-l) and the like can also be stabilized with the subject stabilizer combinations. Both the so-called low density and high density or high crystallinity POIY-OL-OlefiH compositions can be stabilized in accordance with the invention. Reference is made to Fawcett et al. US. Patent No. 2,153,553, granted April 11, 1939, and to copending applications Coover U.S.

Serial No. 559,536, filed January 17, 1956, now abandoned, and Coover et al. US. Serial No. 724,904, filed March 31, 1958, now abandoned, with regard to the prepartion of various poly-a-olefin compositions that can be stabilized against thermal degradation in accordance with the invention. The additive stabilizer combinations of the invention are especially useful for stabilizing the solid resinous poly-a-olefins having average molecular weights of at least 15,000 and more usually at least 20,000, although the stabilizer combinations of the invention can also be utilized to stabilize the so-called poly-ecolefin waxes having lower average molecular weights of usually 3,000 to 12,000.

The amount of the combination of the diester of 3,3- thiodipropionic acid, the alkylidenebisphenol and the phenyl salicylate employed in POIY-Ot-Olfifill compositions in accordance with the invention can be widely varied, the stabilizing amount of this combination usually varying with the particular use to which the poly-a-olefin compositions are to be put. Concentrations of about .001%'to 10% and generally about .00l% to 5% for each component of the stabilizer combination are used, with about .01% to 3% being preferred the concentration being based on the weight of the poly-a-olefin.

The stabilizer combinations of the invention can be incorporated or blended into poly-a-olefin compositions hob and dialkyl-3,3'-thiodipropionates.

hanced stability against deterioration resulting from exposure to sunlight or ultraviolet light. Thus, poly-aolefins stabilized in accordance with the invention have an extended life expectancy and can be used more efiectively than unstabilized poly-a-olefins for a wide diversity of uses. Poly-a-olefins stabilized as described can be cast, extruded, rolled or molded intosheets, rods, tubes, pipes, filaments and other shaped articles, including the widely used films of the polymers about .5 to 100 mils in thickness. The present compositions can be used for coating paper, wire, metal foil, glassfiber fabrics, ,synthetic and natural textiles or fabrics, and other such materials.

While phenyl salicylates are effective additives in polym olefins for minimizing deterioration resulting from exposure to ultraviolet light, such additives individually do not significantly improve poly-a-olefins with respect to resistance to deterioration resulting from exposure to elevated temperatures. Similarly, combinations'of phenyl salicylates and dialkyl-3,3-thiodipropionates do not significantly improve polya-olefins with respect to resistance to' deterioration resulting from exposure to elevated temperature.- Joyner, Shearer and Tholstrup, in copending application Serial No. 850,985, filed November 5, 1959,

described poly-a-olefins having improved thermal stability containing synergistic combinations of alkylidenebisphe- I have now found that when phenyl salicylates are added to the combinations described by Joyner, Shearer and Tholstrup, an improved three-component synergistic stabilizer system results. The stabilizing effect with respect to thermal stability in poly-u-olefins of the stabilizer'combinations of the invention is substantially greater then the additive eflect of the individual components of such stabilizer combinations.

To the poly-a-olefin compositions of the invention can also be added minor proportion amounts, usually about .001% to by weight basedon the poly-:x-olefin, of zinc stearate, calcium stearate, sodium stearate or an organic phosphite such as those described in the Joyner and Coover copending application, Serial, No. 681,897, filed September 4, 1957, now abandoned.

The invention is illustrated by the following examples of preferred embodiments thereof. In the following examples, the stability of the poly-ot-olefins was determined by, an oven storage test. Thepoly-a-olefin under investigation'iscompression: molded 'into' a smooth sheet or .plate. The 'plate' is then cut into pieces weighing about 0.25 g. each. The 0.25 g. samples of the molded polymer are then placed in an air oven at 160 C. Samples are removed at intervals and each sample analyzed for peroxides. .The oven storage life isthc time required for initial peroxide formation in a sample of the polymer. To determine peroxide formation in the oven exposed samples, each'0.25 g. sample in question is dissolved or suspended in ml. of carbon tetrachloride and allowed 1 to digestfor minutes. To this is added 20 mlfof a mixture consisting of 50% glicialacetic acid and 40% f'chloroform; and then 1.0 ml. of a saturatedaqueous with 0.002 N sodium thiosulfate. The peroxide concentration, P, in milliequivalents per kilogram of polymer is given by the expression, P=8S, where S is the number of milliliters of 0.002 N sodium thiosulfate used.

EXAMPLE 1 Samples of powdered polypropylene were mixed with several stabilizer combinations of the invention as well as with sub-combinations and individual stabilizers comprising such stabilizer combinations of the invention, compresson molded into plates inch in thickness, and the resulting molded samples evaluated with respect to thermal stability by the 160 C. oven storage test described above. The polypropylene was a plastic grade solid poly- Table A Additive: Oven life at 160 (3., hours (1) None 0.2 22; 0.1% DLT'DP 1 3 0.1 4,4- 11 butylidenebis(3-methyl-6-tert.-

butylphenol) 5 54) 1.0% phenyl salicylate 1 5) 1.0% p-tert.-butylphenyl, 5-tert.-butyl salicylate 0.5 26) 1.0% p-tert.-octylphenyl salicylate 1 7) 1.0% phenyl sal1cylate+0.1% DLTDP 1 (8) 1.0% p-tert.-octylpheny1 salicylate+0.1%

DLTDP 1 (9) 1.0% phenyl, 3-pl1enyl salioylate+0.1%

DLT 1 (10) [0.1% 4,4'-n-butylidenebis(3-methyl-6-tert.-

V butylphenol) +01% DLTDP1=A 100 (11) A-l-l 0% phenyl salicylate 240 (12) A+1 0% p-tert.-octylphenyl saltcylate 240 (13) A+1.0% phenyl, S-phenyl salicylate 250 (14)A+1.0% p-tert-butylphenyl, 5-tert.-buty1 salicylate 220 In the above table, the octyl radical of the p-tert.-octylphenyl salicylate was a l,l,3,3-tetramethylbutyl radical. While phenyl salicylates are effective ultraviolet inhibitors in poly-a-olefins, such materials are inetfective heat stabilizers. Hence, it was unexpected when the addition of a phenyl salicylate to the combination'of a dialkyl-3,3'- thiodipropionate and an alkylidenbisphenol was found to be an outstanding stabilizer combination in POIY-zx-OlfifiIlS against thermal degradation. Such was particularly unexpected in view of the fact that the combinations of phenyl salicylates and dialkyl-3,3-thiodipropionates are ineffective heat, stabilizers. Similar synergism as that demonstrated in Table A is also demonstrated if plastic grade solid polyethylene'having an average molecular weight greater than 15,000, a density of about .91 and a ipionate, or if thevarious combinations of dialkyl-3,3-

thiodipropionates and alkylidenebisphenols described in the copending application by Joyner, Shearer and Th0lstrup, Serial No; 850,985, filed November 5, 1959, are substituted for the combinationsof dilauryl-3,3'-thiodipropionate and 4,4f n butylidenebis(3-methyl-6-tert.-buty1- phenol), in the described stabilizationevaluations.

, EXAMP E? 7 Several samples of polypropylene as described in Example 1 containing various stabilizer combinations of the invention and including calcium stearate were evaluated solution of potassium iodide. Theresulting mixture is V V 'all'owed toreact for two minutes, mlxofwater added to dilute the mixturejand then a starch indicatojr' is added. Theresulting mixture is then back titr ated propionate. 75

with respect to thermal stability by the C. ovenstorage test as described in Example 1. The results of the test are summarized bythe data set out in Table B below. In Table B, DLTDP designates dilauryl-3,3'-thiodi- The concentrations in Table B are based on the weight of the polypropylene.

Table B Oven life at Additive 160 0., hours (1) None 0.2 2) 0.1% DLTDP 1 3) 0.1% 4,4- 11 butylidenebis(3-methyl-6-tert.-

butylphenol) (4) 0.05% calcium stearate 1 5) 1.0% ptert-octylphenyl salicylate 1 (6) 1.0% phenyl, 3-phenyl salicylate 1 (7) 1.0% p-tert.-butylphenyl, 5-tert.-butylsalicylate 1 (8) 1.0% p-tert.-octylphenyl salicylate+ 0.1%

DLTDP 1 (9) 1.0% phenyl, B-phenyl salicylate+0.l%

DLTDP 1 (10) [0.1% 4,4-n-butylidenebis(3-methyl-6-tert.-

butylphenol) +O.1% DLTDP+0.05% calcium stearate] :B 140 (11) B+1.0% p-tert.-octylphenyl salicylate 250 12) B+1.0% phenyl, 3-phenyl sa1icy1ate 250 (13) B+1.0% p-tert.-butylphenyl, 5-tert.-butyl salicylate 250 (14) B+1.0% resorcinol monobenzoate 80 In Table B, the octyl radical of the p-tert.-octylphenyl salicylate was a l,1,3,3-tetramethylbutyl radical. The inefiectiveness of resorcinol monobenzoate (item 14, Table B) as compared to the closely related phenyl salicylate components of the invention further illustrate the unobviousness of the present invention.

EXAMPLE 3 A stabilizer combination of the invention in polypropylene was evaluated with respect to thermal stability by the method described in Example 1 except that the polypropylene had an inherent viscosity of 1.74 as determined intetralin at 145 C. The results of the stability evaluation are summarized by the data set out in Table C below. In Table C, DLT DP designates dilauryl-3,3'-thiodipropionate. The concentrations in Table C are based on the weight of the polypropylene.

Table C Oven life at Additive: 160 0., hours (1) None 0.2 (2) 0.05% 4,4-n-butylidenebis(3 methyl-(Hertbutylphenol) 5 (3) 0.1% DLTDP 1 (4) 0.05% calcium stearate 1 (5) 1.0% p-tert-octylphenyl, 5-tert.-butyl sali- O 2 cy (6) 0.1% DLTDP+1% p-tert.-octylphenyl, 5-

tert.-buty1 salicylate 1 57) 0.1 DLTDP+ 0.05 calcium stearate 2 S) [0.05% 4,4-nbutylidenebis(3methyl-6-tert.- butylphenol) +0.1 DLTDP+0.05 calcium stearate] C 110 (9) (B+1.0% ptert.octylphenyl, 5-tert. -butyl salicylate 280 In Table C, the octyl radical of the p-tert.-octylphenyl, 5-tert.-butyl salicylate was a 1,1,3,3-tetramethylbutyl radical.

vThe present invention thus provides novel poly-a-olefin compositions having improved stability against deterioration resulting from exposure to elevated temperautres, and particularly, it provides novel synergistic stabilizer combinations for poly-a-olefin compositions.

Although the invention has been described in detail with reference to preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined by the appended claims.

I claim:

1. A solid poly-a-olefin composition comprising a solid poly-a-olefin prepared from an a-monoolefinic aliphatic hydrocarbon having 2 to 10 carbon atoms containing a stabilizer combination comprising about .00l% to 10% by weight based on said poly-a-olefin of a diester of 3,3- thiodipropionic acid having the formula wherein R is an alkylradical having 4 to 20 carbon atoms; about .001% to 10% by weight based on said poly-u-olefin of an alkylidene-bisphenol, and about .001% to 10% by weight based on said poly-a-olefin of a phenyl salicylate, said alkylidenebisphenol having the formula wherein R is an alkylidene radical having 1 to 12 carbon atoms and R R R and R are alkyl radicals having 1 to 12 carbon atoms, and said phenyl salicylate having the formula on Q Q R5 R7 O S(OH2CH2% O R):

wherein R is an alkyl radical having 4 to 4 carbon atoms; (b) about .001% to 10% by weight based on said poly-aolefin of an alkylidenebisphenol having the formula wherein R is an alkylidene radical having 1 to 12 carbon atoms and R R R and R are alkyl radicals having 1 to 12 carbon atoms; and (c) about .001% to 10% by Weight based on said poly-a-olefin of a phenyl salicylate having the formula wherein R and R are selected from the group consisting of hydrogen atoms, alkyl radicals having 1 to 15 carbon atoms and cyclic hydrocarbon radicals having 6 to 12 carbon atoms.

3. A solid poly-a-olefin composition comprising solid polyethylene containing a stabilizer combination comprising: (a) about .00l% to 5% by weight based on said polyethylene of a diester of 3,3'-thiodipropionic acid having the formula wherein R is an alkyl radical having 8 to 18 carbon atoms; (b) about .001% to 5% by weight based on said polyethylene of an alkylidenebisphenol having the formula wherein R is an alkylidene radical having 1 to 12 carbon atoms and R R R and R are alkyl radicals having 1 ,to 12 carbon atoms; and (c) about .001%. to 5% by v butylidenebis 3 -methyl-6-tert;-butylphenol) 7 weight based on said'polyethylene of a phenyl salicylate having the formula wherein R is an alkyl radical having 8 to 18 carbon atoms; (b) about .00'1% to% by weight based on said polypropylene of an alkylidenebisphenol having the formula wherein R is an alkylidene radical having 1 to 12 carbon atoms and R R R and R are alkyl radicals having 1 to 12 carbon atoms; and (c) about 001% to 5% by weight based on said polypropylene of a phenyl salicylate having the formula V wherein R and R are selected from the group consisting of hydrogen atoms, alkyl radicals having 1 to carbon atoms and cyclic hydrocarbon radicals having 6 to 12 carbon atoms.

6. A composition 'as described in claim 3 wherein the diester of 3,3'-thiodipropiohic acid is dilauryl-3,3-thiodi propionate.

7. A solid POIY-Ot-Olfifill composition comprising solid polypropylene containing a stabilizer combination comprising about .01% to 3% by weight based on said polypropylene of.dilauryl-3Q3'-thiodipropionate, about .0l%.

to 3% 'by weight based on 'said polypropylene of 4,4-

and about .01% to 3% by weight based on said polypropylene of a phenyl salieyla-te selected from the group consisting 3% by weight based on said polyethylene of 4,4'n-butyl idenebis(3-methyl 6 tert.-butylphenol) and about .01%

' 10. A solid poly-a-olefin composition comprising solid polyethylene containing a stabilizer combination comprising about .01% to 3% by weight based on said polyethylene of dilauryl-3,3-thiodipropionate, about .01% to 3% by weight based on said polyethylene of 4,4'-n-butylidenebis(3-methyl-6-tert.-butylphenol) and about .01 to 3% by weight based on said polyethylene of p-tert.- octylphenyl, 5-tert.-butyl salicylate.

11. A solid POlY-a-Olefin composition comprising solid polyethylene containing a stabilizer combination comprising about .0l% to 3% by weight based on said polyethylene of dilauryl-3,3'-thiodipropionate, about .0l% to 3% by weight based on said polyethylene of 4,4-n-butylidenebis(3-methyl-6-tert.-butylphenol) and about .01 to 3% by weight based on said polyethylene of phenyl, 3- phenyl salicylate.

12. A solid poly-ot-olefin composition comprising solid polyethylene containing a stabilizer combination compris ing about .01% to 3% by weight based on said polyethylene of dilauryl-3,3'-thiodipropionate, about .01% to 3% by weight based on said polyethylene of 4,4-n-butylidenebis(3-methyl-6-tert.-butylphenol) and about .01% to 3% by weight based on said polyethylene of p-tert.- butylphenyl, 5-tert.-butyl salicylate.

13. A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising about .01% to 3% by weight based on said polypropylene of dilauryl-3,3-thiodipropionate, about .01% to 3% by weight based on said polypropylene of 4,4-n butylidenebis(3-rnethyl-6-tert.-butylphenol) and about .01% to 3% by weight based on said polypropylene of phenyl salicylate.

14. A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising about .0l% to 3% by weight based on said polypropylene of dilauryl-3,3'-thiodipropionate, about .01% to 3% by weight based on said. polypropylene of 4,4-nbutylidenebis(3-methyl-6-tert.-butylphenol) and about .01% to 3% by weight based on said polypropylene of ptert.-octylphenyl salicylate.

15. A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising about .01% to 3% by weight based on said polypropylene of dilauryl-3,3.'-thiodipropionate, about .0l% to 3% by weight based on said polypropylene of 4,4-nbutylidenebis(3-methyl-6-tert.-butylphenol) and about .01% to 3% by weight based on said polypropylene of p-tert.-octylphenyl, 5-tert.-butyl salicylate.

16. A solid'poly-a-olefin composition comprising solid 7 polypropylene containing a stabilizer combination comprising about .01% to 3% by Weight based on said polypropylene of dilauryl-3,3-thiodipropionate, about .01% to 3% by Weight based on said polypropylene of 4,4'-nbutylidenebis(3-methyl-6-tert.-butylphenol) and about .O1% to 3% by weight based on said polypropylene of phenyl, 3-pheny-l salicylate.

- propylene of dilauryl-S,3-thiodipropionate,' about 01%.

to 3% by weight based .on said'polyethylene of phenyl.

salicylate. V

9. A solid poly-:i-olefin composition comprising solid polyethylene containing a stabilizer combination compris} ihgabout .01% to 3% by weight based on said poly- 17. A solid poly-a-olefin composition comprising solid polypropylene containing a stabilizer combination comprising about .01% to 3% by weight based on said polyto 3% by weight based on said polypropylene of 4,4-nbutylidenebis(3-methyl-6-tert.-butylphenol) and about .0l% to 3% by weight based on said polypropylene of ptert.'-butylphenyl, 5-tert.-butyl salicylate} V References Cited in the file of this patent UNITED STATES. PATENTS 2,514,216 Stefl July 4, 1950 7 2,519,755 onbbin tt Aug.. 22, 1950 25568902 Thompson etal. V Sept. 25, 1951 2,859,194 Reid a a1. Nov. 4, 1958 Dietzler f Dec. 15, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,033,814 May 8, 1962 Clarence E. Tholstrup It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6 line 32., for "4 to 4" read 4 to 20 Signed and sealed this 9th day of October 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A SOLID POLY-A-OLEFIN COMPOSITION CONPRISING A SOLID POLY-A-OLEFIN PREPAREDF FROM AN A-MONOOLEFINIC ALIPHATIC HYDROCARBON HAVING 2 TO 10 CARBON ATOMS CONTAINING A STABLIZER COMBINATION COMPRISING ABOUT .001% TO 10% BY WEIGHT BASED ON SAID POLY-A-OLEFIN OF A DIESTER OF 3,3'' THIODIPROPIONIC ACID HAVING THE FORMULA 